Modular Construction of Nanostructured Catalysts for Solar Hydrogen Generation from Water

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CBET-0829142OsterlohThe sunlight that strikes the earth over one hour provides enough energy to satisfy all human energy needs for an entire year. However, efficient methods of conversion of this energy into usable fuels have yet to be found. Of particular interest in this regard are materials that use light to photochemically split water into oxygen and hydrogen. The hydrogen then serves as an environmentally friendly energy carrier. Many inorganic materials are known to catalyze this "water splitting reaction", but their efficiency remains too low for commercial applications. The purpose of this project is twofold. First, a new class of water splitting catalysts will be developed that can be assembled in a modular fashion from inorganic nanoparticles. Here, the nanoparticles function as separate components for light absorption and water conversion. The advantage of this building block approach is that light absorption, charge transfer, and chemical properties can be independently optimized. The final catalysts are powders that can be mixed in water to produce clean hydrogen from abundant solar energy. The second goal of the project is to learn more about the mechanism of photochemical water splitting with nanoparticle catalysts. A first step here will be to measure the amount of evolved hydrogen and oxygen under ultraviolet or visible light illumination, and to correlate gas production with the structure of the catalysts. Secondly, time-resolved absorption spectroscopy will be employed to determine how effectively light is converted into charge and how quickly the charge travels to the surface of the catalysts, where water conversion takes place. The effectiveness of the nanoparticle surfaces to split water will be studied separately using electrochemical methods. Similar methods will also be used to determine the electronic structure of the nanoparticle components, which control the flow of charge within the catalysts. The results from these studies will improve the understanding of the catalytic activity of inorganic nanostructures, and help to raise their efficiency. The research portion of this project will be accompanied with several educational and outreach activities, including a new graduate class "Chemistry of Nanoparticles" and science exhibits and chemistry shows for the public. New opportunities for graduate and undergraduate student research will also be created. These activities are designed to recruit and educate a new generation of scientists and engineers who can help to develop more effective ways to utilize sunlight as a renewable energy source.